Data networks with mobile devices are well known. In such data networks, mobile devices such as laptop computers can be attached at any point in the network. In the case of data networks employing the well-known Internet Protocol (IP), data is subdivided into packets which are routed in the network using IP addresses that are related to the topology of the network. Each device in the network is assigned one or more IP addresses. The IP addresses are partially determined by what portion of the network the device is connected to. This presents a problem for mobile devices since they may be connected anywhere in the network. Generally, mobile devices retain the same “home” IP address regardless of where they are presently connected in the network. However, when the device is away from its home network, it will be unable to receive packets addressed to the home address unless those packets are forwarded to a care-of-address associated with the device's present location. The device may also receive packets sent directly to a care of address. The care of address is defined by a protocol known as mobile IP protocol (or “Mobile IP”). Presently, there are two different versions of mobile IP, version 4 (“MIPv4”) and version 6 (“MIPv6”).
There is shown in FIG. 1 a data network 100 that employs Mobile IP to facilitate the mobility of mobile devices. The data network 100 is composed of a number of interconnected subnetworks 103-106. In the data network 100, data is transmitted in packets between a number of devices 130-138 via routers 116-120. The routers 116-120 direct the data packets to the proper subnetwork 103-106 of the data network 100 so that they reach the proper destination device. A mobile device 134 is shown attached to the data network 100. Although the mobile device 134 is shown attached to the subnetwork 104, it should be understood that it may be moved to any location within the data network 100. The data network 100 also contains a call control entity 138. The call control entity 138 manages calls between different devices in the data network 100. These calls may be similar to telephone calls or they may be multimedia sessions such as streaming video or audio, video conferences, game sessions etc.
In one embodiment, the data network 100 employs MIPv4 to route data packets to the mobile device 134. Alternatively, the data network 100 employs MIPv6 to route data packets to the mobile device 134. Under either MIPv4 or MIPv6, every mobile device is assigned a home agent on a home network. In FIG. 1, a home agent 130 for the mobile device 134 is shown attached to the subnetwork 103, which is a home subnetwork for the mobile device 134. All subnetworks that are not the home subnetwork of the mobile device 134 are referred to as foreign subnetworks. In MIPv4, each foreign network is assigned a foreign agent. In FIG. 1, a foreign agent 139 is shown attached to subnetwork 104, which is a foreign subnetwork of the mobile device 134. The mobile device 134 has an IP address (i.e., “home” address) that corresponds to the home network 103. When a device in the data network 100 sends a data packet to the mobile device 134 that is addressed to the home address, the data packet is directed by the routers 116-120 to the home network 103 of the mobile device 134. If the mobile device 134 is not attached to the home subnetwork 103, packets addressed to the home address are intercepted by the home agent and forwarded to the foreign agent 139 on the subnetwork 104. The foreign agent 139 then passes the data packet to the mobile device 134. Using this process, the mobile device is able to keep the same IP address as it moves about the data network 100 even through the IP address corresponds to a location on the home subnetwork 103.
In the embodiment where the data network 100 employs MIPv6, there are no foreign agents. Upon receiving packets addressed to the mobile device's home address, the home agent 130 sends the data packets destined for the mobile device 134 directly to the mobile device 134. In addition, MIPv6 provides for the mobile device receiving a care of address when it is away from its home network. Packets that are addressed to the care of address are routed directly to the mobile device 134 instead of having to be intercepted by the home agent 130 and forwarded. Packets are typically sent as part of a “session,” or series of packets exchanged between devices. A session may represent, for example, a download of a webpage, a multi-media call, or an FTP session. When a session is set up, the sending device typically does not know that the mobile device has moved from its home address, so the first packets of the session are sent to the mobile device's home IP address, intercepted by the home agent and forwarded to the mobile device. The mobile device 134 may then inform the sending device of its care of address, so that the sending device may send data packets directly to the mobile device 134.
The call control entity 138 manages the setup of calls between devices in the data network 100. Setting up a call establishes a session between two or more mobile or fixed devices so that they may exchange messages such as, for example, voice, video, data or gaming media. This requires that the call control entity 138 be able to signal the devices in order to invite them into the call. It also requires that communication resources can be allocated to carry the media.
One problem that arises when setting up calls involving mobile devices is that excessive time delays may result when messages are routed to the mobile device 134 by way of the home agent 130. The time delay can be particularly problematic in large networks where the mobile device 134 may be a long distance from the home agent. This problem is most significant in MIPv4, because all data packets from the call control entity 138 to the mobile device 134 are sent to the home agent 130 first. In MIPv6, typically only the first data packet (s) of a session between the call control entity 138 to the mobile device 134 are sent to the home agent 130. However, this still results in a delay in the call setup.
A second problem arises when an attempt is made to allocate the communication resources in a data system that employs Mobile IP. Mobility protocols provide location transparency that hides the actual location of the devices, preventing the call control entity 138 from determining which resources the mobile devices require.
Therefore, there is a need for a method of decreasing the setup time required for calls made in a data network containing mobile devices. There is further a need for informing a call control entity of the data network of the location of mobile devices, so that it is able to determine which resources the mobile devices require. This invention is directed to satisfying or at least partially satisfying these needs.